Library unit and magazine position detecting method in the library unit

ABSTRACT

A library unit of the present invention includes a magazine, a cartridge, at least one sensor and an accessor. The cartridge is loaded in the magazine and arranged in a direction in which the magazine is loaded to or unloaded from the library unit. The sensor is provided for the library unit and activated to make an output, when the magazine is pulled out to a predetermined position, whether or not the magazine is positioned facing the sensor. The accessor identifies a position of the magazine according to an output of the sensor and receives the cartridge.

BACKGROUND OF THE INVENTION

The present invention relates to a library unit and a magazine positiondetecting method in the library unit, and more particularly to a libraryunit in which an accessor can access any cell of a magazine left in thelibrary unit by detecting the position of the magazine which is pulledout halfway, as well as a magazine position detecting method in thelibrary unit.

There have been proposed various types of methods for positioning atransferring mechanism in a magnetic tape library unit so far.

For example, Japanese Unexamined Patent Publication No.Hei04(1992)-319564 (patent document 1) discloses one of such methods.According to the method, a reflection sensor attached to a mediumtransferring mechanism (accessor) detects an end or reading mechanism ofa cell which loads a medium (tape cartridge). A flag sensor provided forthe accessor detects a reference pattern on the flag provided inparallel to a spline for guiding the accessor. The intervals of pulsesoutput from both reflection sensor and flag sensor is measured with useof output pulses of an encoder. The output pulses of the encoderindicate the number of rotations of a motor for driving the accessor.The measuring result is stored in a memory. And during normalpositioning, the position at which the motor stops is controlledaccording to the positional data of the cell read from the memory.

FIG. 11 shows a block diagram of a large capacity external storage unit(magnetic tape library unit) 1100 disclosed in the patent document 1.

The library unit 1100 includes plural cells 1120 for loading pluralmedia 1110; plural reading or writing mechanisms (magnetic tape drives)(not shown) for writing data to or reading data from the plural magnetictape cartridges; an accessor 1130 for storing each tape cartridge 1110in or taking out it from each cell 1120 and each magnetic tape drive; aspline 1140 for guiding the accessor 1130; a motor 1150 for driving theaccessor 1130; a positioning reference flag 1160 provided in parallel tothe spline 1140; a flag sensor 1170 for reading a reference pattern onthe flag 1160; and an encoder 1180 for outputting the number of pulsesproportionally to the number of rotations of the motor 1150. In anotheraspect of the invention, the library unit further includes a reflectionsensor 1190 attached to the accessor 1130 and used to detect an endsurface of each cell 1120; a counter 1101 for counting output pulses ofthe encoder 1180 while the accessor 1130 is moving; a non-volatilememory 1102 for storing the count of the counter 1101 in relation to theposition of each cell 1120; computing means (computer) 1103 forcomputing a difference between the data in the memory 1102 and apredetermined reference value to control the accessor 1130 bycontrolling the motor 1150.

In the magnetic tape library unit 1100, the counter 1101 counts thenumber of pulses outputted from the encoder 1180 between when the endsurface of a cell is detected by the reflection sensor 1190 and when thereference pattern is detected by the flag sensor 1170 at the time ofperiodical inspection. The count value is stored at an address in thememory 1102 corresponding to the position of the cell 1120.

When the accessor 1130 moves and the flag sensor 1170 detects thepositioning reference pattern of the flag 1160, the computer 1103 readsthe target cell position data from the memory 1102 to compute adifference from the reference value. The difference indicates a relativedeviation between the flag 1160 and the target cell 1120 or between theflag 1160 and the target magnetic tape drive. The computer 1103 correctsa predetermined value according to the result of the computing. Then,the computer 1103 controls the motor 1140 so as to stop at a positionwhere the number of pulses outputted from the encoder 1180 matches withthe corrected value.

Consequently, because such a relative positional deviation can becorrected in the library unit 1100 disclosed in the patent document 1,the accessor 1130 can be controlled accurately in positioning.

SUMMARY OF THE INVENTION

In the case of the related library unit, when all the cells (magazines)are set completely in the library unit, the accessor can be controlledaccurately in positioning. If a magazine is pulled out halfway, however,it is not possible to identify where the magazine will stop and theaccessor cannot access a cartridge in the magazine. This has been aproblem.

An object of the present invention is to provide a library unit and amagazine position detecting method in the library unit which enables itsaccessor to access cells in a magazine pulled out halfway and left inthe library unit by detecting the position of the magazine.

According to one aspect of the present invention, the library unit isprovided which includes a magazine loaded in the library unit, acartridge which is loaded in the magazine and arranged in a direction inwhich the magazine is loaded or unloaded, at least one sensor providedfor the library unit and activated to make an output, when the magazineis pulled out to a predetermined position, whether or not the magazineis positioned facing the sensor, and an accessor which identifies aposition of the magazine according to an output of the sensor and whichreceives the cartridge.

According to another aspect of the present invention, a magazineposition detecting method in the library unit which has a magazineloaded, a cartridge, which is loaded in the magazine and arranged in adirection in which the magazine is loaded/unloaded, at least one sensor,and an accessor for receiving the cartridge, concludes making an outputof whether or not the magazine is positioned to face the sensor byactivating a output of the sensor when the magazine is pulled out to apredetermined position and identifying a position of the magazineaccording to the output of the sensor to access the cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be made moreapparent by the following detailed description and the accompanyingdrawings, wherein:

FIG. 1A is a schematic perspective view of a magnetic tape library unitin first and second exemplary embodiments of the present invention;

FIG. 1B is a perspective view of a cell which is cut off partially;

FIG. 2 is a block diagram of an accessor controller in the firstexemplary embodiment;

FIGS. 3A and 3B are top views of the magnetic tape library unit in thefirst and second exemplary embodiments of the present invention;

FIGS. 4A and 4B is a perspective view of a locking mechanism of themagnetic tape library unit in the first and second exemplary embodimentsof the present invention;

FIGS. 5A through 5D illustrate the operation of the magnetic tapelibrary unit in the first and second exemplary embodiments of thepresent invention;

FIGS. 6A and 6B shows position information of the magazine and statusinformation of the sensors shown in FIGS. 5A through 5D;

FIGS. 7A through 7D show contents of the magnetic tape information tableshown in FIGS. 5A through 5D;

FIGS. 8A and 8B show contents of the magnetic tape information tableshown in FIGS. 5A through 5D when a cartridge is moved;

FIG. 9 is a block diagram of the accessor controller in the secondexemplary embodiment of the present invention;

FIG. 10 shows how address information is translated in the secondexemplary embodiment of the present invention; and

FIG. 11 is a block diagram of a related magnetic tape library unit.

In the drawings, the same reference numerals represent the samestructural elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

At first, a first exemplary embodiment of the present invention will bedescribed in detail below.

Referring to FIG. 1A, the library unit 100 includes two magazines 120composed of plural cells 110 for loading a tape cartridge, respectively;a magnetic tape drive 130 for reading data from or writing data to arecording medium (magnetic tape) in each cartridge; and an accessor 140which gives each tape cartridge to the magazine 120 or the magnetic tapedrive 130, and receives each tape cartridge from the magazine 120 or themagnetic tape drive 130. The plural tape cartridges are loaded in thecells 110, respectively, so as to be stacked horizontally. FIG. 1B showsa perspective view of a partially cut-off cell 110 of a magazine 120.

The accessor 140 can move freely into the depth (X direction) of thelibrary unit 100. The accessor 140 has functions for giving andreceiving each tape cartridge between the magazines 120 and the magnetictape drive 130 and between the two magazines 120. A magazine 120 ismoved in the X direction to be loaded in or unloaded from the libraryunit 100.

The library unit 100 has plural sensors at its internal wall. Accordingto the detection result of each of the sensors, it is possible todetermine a position of each cell 110 of a magazine 120 pulled outhalfway from the library unit 100. The position for attaching each ofthe sensors and how the sensor detects a position of each cell will bedescribed in detail later.

The library unit 100 has an internal plane 101 that is in parallel to adirection for attaching or removing itself 100 and adjacent to eachmagazine 120. Plural locking mechanisms are provided on the internalplane 101. When a magazine 120 is pulled out halfway from the libraryunit 100, plural locking mechanisms are turned on or off according tothe position of the magazine 120. The height of the internal plane 101may be free as long as it does not disturb the accessor 140 to accesseach cell 110. The locking mechanism will be described in detail later.The magnetic tape drive 130 is controlled by a drive controller 131 (notshown).

As shown in FIG. 2, the accessor 140 is controlled by an accessorcontroller 141. The accessor controller 141 includes a CPU 143 and amemory 142. The memory 142 stores magazine position information 121, amagnetic tape information table 122, and sensor status information 123.The magazine position information 121 shows the position status of eachmagazine pulled out from the library unit 100. The sensor statusinformation table 123 shows a relationship between the ON/OFFinformation of each of the sensors of the library unit 100 and theposition status of each magazine. The magnetic tape information table122 stores the correspondence between addresses of cells 110 andmagnetic tape drives 130 and magnetic tape identification information.The information is used to determine the position of each cell 110 of apulled-out magazine. The magazine position information 121, the magnetictape information table 122, and the sensor status information 123 willbe described in detail later.

When a magazine 120 is pulled out halfway from the library unit 100, thelocking mechanism is turned on or off according to the position of themagazine 120. Receiving the locking mechanism on or off information, theCPU 143 of the accessor controller 141 activates the sensors only whenthe locking mechanism is turned on. Receiving the detected sensor on oroff information, the CPU 143 refers to the sensor status information 123to identify the magazine position status. Then, the CPU 143 updates themagnetic tape information table 122 automatically.

When the magnetic tape identification information is specified by such ahost system as a host computer, the CPU 143 of the accessor controller141 refers to the magnetic tape information table 122 to identify theaddress of the cell 110 in which the magnetic tape specified by themagnetic tape identification information is loaded. Then the CPU 143controls the accessor 140.

In many cases, a label (VOL) is written in the first data block of eachmagnetic tape. The label (VOL) identifies the magnetic tape. Theidentification information used in this exemplary embodiment means sucha label (VOL).

The library unit 100 of the present invention may include two or moremagnetic tape drives 130. In this case, the library unit 100 can alsohave functions for giving and receiving tape cartridges between or amongthose tape drives 130.

The library unit 100 of the present invention may also have three ormore magazines 120.

The library unit 100 of the present invention may also have two or moreaccessors 140.

Referring to FIG. 3A, each magazine 120 has a partition 300 forpartitioning each cell 110 from another in the row direction. And anotch 310 is provided at the bottom board at each partition 300 of eachmagazine 120. The notch 310 is shaped as a trapezoid having a short sideat the partition side. The partition 300 may be provided only betweencells 110 without being provided at an end of the magazine 120.

A sensor 320 is provided at a position on the inner wall of the libraryunit 100 so as to face the partition 300 when the magazine 120 is loadedin the library unit 100. The sensor 320 is a reflection type photosensorand includes a light emission part and a light receiving part. If amagazine 120 is positioned facing the sensor 320, the light emitted fromthe light emission part is reflected by the magazine 120 and thereflected light is received by the light receiving part. When thereceiving part of the sensor 320 receives a reflected light, theaccessor controller 141 confirms the existence of a magazine 120 at aposition facing the sensor 320 and stores the information in the memory142. And a locking mechanism 330 is provided on the internal plane 101of the library unit 100 of the present invention. The locking mechanism330 fixes the accessor 140 at a position where the accessor 140 canaccess a target cell 110 when the magazine 120 is to be pulled out inthe X direction.

FIG. 4 shows a perspective view of the locking mechanism 330 of thelibrary unit 100 of the exemplary embodiment. The locking mechanism 330is a momentary type one and is turned on or off when the projection 400is moved in the Y direction. The projection 400 is shaped as a trapezoidwhich has a short side at the contact side with the magazine 120 and hasa long side at the side of the internal plane. The projection 400 is fitin a notch 310 of the magazine 120. Because the projection 400 is shapedas a trapezoid (not a rectangle), the locking mechanism 330 is turned onor off more easily when the magazine 120 is pulled out in the Xdirection.

When the projection 400 comes to face a notch 310 of the magazine 120which is pulled out in the X direction, the projection 400 protrudes asshown in FIG. 4A and the locking mechanism 330 begins to work. On theother hand, in case where the projection 400 does not face a notch 310of the magazine 120, the projection 400 is pressed down onto a sidesurface of the bottom board of the magazine 120 as shown in FIG. 4B andthe locking mechanism does not work at this time.

The projection 400 and the notch 310 of the magazine 120 may not beshaped as trapezoids; they may be shaped freely if they are almostsimilar in shape and the locking mechanism 330 is turned on or off whenthe magazine 120 is pulled out.

FIG. 5 shows the operation of the library unit 100 when a magazine ispulled out in the X direction. In this first exemplary embodiment,cartridges 200 and 201 are loaded in the cells 111 and 114,respectively.

As shown in FIG. 5A, when a magazine 120 is loaded in the library unit100, the projections of the locking mechanisms 331 to 334 are protrudedand fit in the notches 310 of the magazine 120.

As shown in FIG. 5B, when a tape cartridge 200 is taken out from thecell 111, the magazine 120 is pulled out in the X direction. And when itbegins to pull out the magazine 120, the projections 400 of theprotruded locking mechanisms 331 to 333 are pressed down onto a sidesurface of the magazine 120.

As Shown in FIG. 5C, because the locking mechanisms 331 to 334 aremomentary type ones, the projection 400 of each of the lockingmechanisms 331 to 334 protrudes again when it meets the next notch 310of the magazine 120.

The library unit 100 checks whether or not the light receiving part ofeach of the sensors 321 to 324 receives a light only when the lockingmechanisms 331 to 334 are protruded. More concretely, only when theprojection 400 of each of the locking mechanisms 331 to 334 isprotruded, each sensor 321 to 324 outputs a signal or a circuit thatsuppresses the outputs of the sensors 321 to 324 does not suppress thoseoutputs. Each of the sensors 321 to 324 is turned on when the libraryunit 100 confirms that its light receiving part receives a light (when amagazine 120 is detected) or turned off when the library unit 100 doesnot confirm that its light receiving part receives a light (when amagazine 120 is not detected).

When a magazine 120 is pulled out and sensor ON or OFF information isdetected, the library unit 100 refers to the sensor status information123 to identify the position status of the magazine 120. Andaccordingly, the magnetic tape information table 122 is updatedautomatically, thereby the position of the target cell is determinedwhen the magazine 120 is pulled out.

In FIG. 5A, all the sensors 321 to 324 are turned on. And if a magazine120 is positioned as shown in FIG. 5B, the library unit 100 does notcheck the status of each sensor 321 to 324. This is because theprojection 400 of each locking mechanism is not protruded at that time.And when the magazine 120 is positioned as shown in FIG. 5C, theprojection 400 of each locking mechanism 331 to 334 is protruded again.Thus the library unit 100 checks the position of the status of eachsensor 321 to 324 to determine the position of the magazine 120. In thiscase, it is detected that the sensors 321 to 323 are turned on and thesensor 324 is turned off. After this, the magnetic tape informationtable 122 is updated automatically and the library unit 100 recognizesthat the cells 112 to 114 are positioned where the cells 111 to 113 havebeen positioned respectively before the magazine is pulled out.

And when the magazine is pulled out and the cells 112 and 113 come outfrom the magazine 120 completely (FIG. 5D), the projection 400 of eachlocking mechanism 331 to 334 is protruded again. Thus the library unit100 checks the status of each sensor 321 to 324. In this case, thesensors 323 and 324 are turned off and the sensors 321 and 322 areturned on. After this, the magnetic tape information table 122 isupdated automatically and the library unit 100 recognizes that the cells113 and 114 are positioned where the cells 111 and 112 have beenpositioned respectively before the magazine 120 is pulled out.

Next, a description will be made in detail for the magazine positioninformation 121, the sensor status information 123, and the magnetictape information table 122 shown in FIG. 5. Here, it is assumed that thepositions of the cells 111 to 114 are represented as A and E when amagazine 120 is loaded in the library unit 100 (FIG. 5A).

The library unit 100 estimates all the possible positions of a magazine120 to be pulled out beforehand and stores those positions as magazineposition information 121 in the memory 142 of the accessor controller140. FIG. 6A shows the contents of the magazine position informationtable 121. Status 1 indicates a case in which the cell 111 is loaded inA, the cell 112 is loaded in B, the cell 113 is loaded in C, and thecell 114 is loaded in D, respectively. Status 2 indicates a case inwhich the cell is loaded in A, the cell 113 is loaded in B, the cell 114is loaded in C, respectively. Status 3 indicates a case in which thecell 113 is loaded in A and the cell 114 is loaded in B, respectively.And status 4 indicates a case in which the cell 113 is loaded in A.

The library unit 100 finds a relationship between the ON or OFFinformation of sensors and the statuses 1 to 4 in magazine positioninformation 121 beforehand and stores the relationship as the sensorstatus information 123 in the memory 142 of the accessor controller 140.FIG. 6B shows the contents of the sensor status information 123. Thestatus 1 indicates a case in which all the sensors 321 to 324 are turnedon (FIG. 5A). The status 2 indicates that the sensors 321 to 323 areturned on and the sensor 324 is turned off (FIG. 5C). The status 3indicates a case in which the sensors 321 and 322 are turned on and thesensors 323 and 324 are turned off (FIG. 5D). And the status 4 indicatesa case in which only the sensor 321 is turned on and the sensors 322 to324 are turned off.

The magazine position information 121 and the sensor status information123 are usually found and stored in the memory 142 when a magazine 120is loaded in the library unit 100 for the first time.

When the magazine 120 is pulled out from the library unit 100 and theON/OFF information of the sensors 321 to 324 is changed, the accessorcontroller 141 refers to the sensor status information 123 to recognizethe position status of the magazine 120. And accordingly, the magnetictape information table 122 is updated automatically.

FIG. 7A through FIG. 7D show the contents of the magnetic tapeinformation table 122 in the statuses 1 to 4, respectively.

The magnetic tape information table 122 is composed of plural recordsand the number of records is equal to a total (m+n) of the number ofmagnetic tape drives (m) and the number of cells (n) provided in thelibrary unit 100. Each record includes fields 700 to 702. The field 700stores cell or magnetic tape drive numbers. The field 701 storesidentification information of the magnetic tapes loaded in the cells 110or magnetic tape drives 130. The field 702 stores addresses to beaccessed by the accessor 140. The identification information 200Aindicates the identification information of a magnetic tape loaded in acartridge 200 shown in FIG. 5. The identification information 201Aindicates the identification information of a magnetic tape loaded inthe cartridge 201 shown in FIG. 5. The addresses 1 to 4 are equivalentto D to A shown in FIG. 5. The address 5 indicates an address of amagnetic tape drive 130 to be accessed by the accessor 140. When nomagnetic tape is loaded in any cell, the identification informationfield 701 is blank. In case where a magazine 120 is pulled out and theaccessor 140 is disabled to access the cell 110, the address field 702is blank. In other words, in case where the address field 702corresponding to the identification information specified by a hostsystem is blank, the accessor 140 cannot access the target tapecartridge (magnetic tape).

In the status 1 shown in FIG. 7A, when the identification information201A is specified by the host system, the accessor controller 141controls so that the accessor 140 accesses the address 1. On the otherhand, when the identification information 200A is specified by the hostsystem, the accessor controller 141 controls so that the accessor 140accesses the address 4.

When the status of the magazine position is shifted to the status 2, themagnetic tape information table 122 is updated automatically as shown inFIG. 7B. At this time, only the address field 702 is updated. When theidentification information 201A is specified by the host system, theaccessor controller 141 controls so that the accessor 140 accesses theaddress 2. Even if the identification information 200A is specified bythe host system, the accessor cannot access any address. This is becausethe address field 702 is blank.

When the status of the magazine position is shifted to the status 3, themagnetic tape information table 122 is updated automatically as shown inFIG. 7C. When the identification information 201A is specified by thehost system, the accessor controller 141 controls so that the accessor140 accesses the address 3. If the identification information 200A isspecified by the host system, the accessor 140 cannot access anyaddress. This is because the address field 702 is blank.

When the magazine position is shifted to the status 4, the magnetic tapeinformation table 122 is updated automatically as shown in FIG. 7D. Whenthe identification information 201A is specified by the host system, theaccessor controller 141 controls so that the accessor 140 accesses theaddress 4. Because the address field 702 is blank, the accessor 140cannot access any address even if the identification information 200A isspecified by the host system.

If the accessor 140 cannot be access the target cell 110, the accessorcontroller 141 notifies the host system of the fact as an error.

Next, a description will be made for the automatic updating of themagnetic tape information table 122 when the tape cartridges 200 and 201are moved by the accessor 140. When the tape cartridges 200 and 201 aremoved to different positions, the identification information field 701is updated in accordance with the new positions (cell or drive numbers).For example, in the state 1, when the accessor 140 moves the cartridge201 from the cell 114 to the cell 113, the magnetic tape informationtable 122 is updated automatically as shown in FIG. 8A. When theaccessor 140 moves the cartridge 200 from the cell 111 to the drive 130in the state 1, the magnetic tape information table 122 is updatedautomatically as shown in FIG. 8B.

In such a way, the library unit in the first exemplary embodiment of thepresent invention can determine the position of the magazine 120 evenwhen the magazine is pulled out halfway, thereby the accessor 140 canaccess the cell 110 left in the magazine 120 pulled out halfway in thelibrary unit 100. Thus the target tape cartridge can be given andreceived by the accessor 140 even when the magazine 120 is pulled outhalfway.

Next, a second exemplary embodiment of the present invention will bedescribed in detail.

In the first exemplary embodiment, the library unit 100 specifiesmagnetic tape identification information. In this second exemplaryembodiment, the library unit 100 specifies the address (physicaladdress) of each cell 110 directly.

In the library unit in this second exemplary embodiment, only theconfiguration of the accessor controller 141 is different from that inthe first exemplary embodiment. Other configuration items are the samein both first and second exemplary embodiments. FIG. 9 shows a blockdiagram of an accessor controller in this second exemplary embodiment.The memory 142 of the accessor controller 141 in this second exemplaryembodiment stores the magnetic tape information table 122 just like inthe first exemplary embodiment. The memory 142 also stores an addresstranslation algorithm corresponding to the number of ON or OFF-statussensors 320 as translation information 900. The memory 142 does notstore any of the magazine position information 121 and the sensor statusinformation 123, however.

Next, the translation information table 900 will be described withreference to the cases shown in FIG. 5. As shown in FIG. 10, thetranslation information 900 includes field 901 to 903. The field 901indicates the fluctuation number of the ON-status sensors and the field902 indicates the fluctuation number of OFF-status sensors. The field903 indicates address translation. Here, the address of a cell n isdefined as n and the smaller the n number is, the more the cell 100 isloaded in the depth of the library unit 100. Address translation to bemade at a change of the detected sensor status can use either the field901 or 902. In the following description, the field 901 indicating thefluctuation number of detected ON-status sensors is used as an example.The information obtained by using the field 902 indicating thefluctuation number of detected OFF-status sensors is shown inparentheses.

In the case of the library unit 100 shown in FIG. 5, when thefluctuation number of detected ON-status sensors decreases by one (thenumber of detected OFF-status sensors increases by one), the magazine120 is pulled out by a one-cell distance from the library unit 100. Inthis case, the address translation field 903 in the translationinformation table 900 therefore stores the address n+1 translated fromthe address n. When the fluctuation number of detected ON-status sensorsdecreases by two (the number of detected OFF-status sensors increases bytwo), the magazine 120 is pulled out by a two-cell distance from thelibrary unit 100. In this case, the address translation field 903 in thetranslation information table 900 therefore stores the address n+2translated from the address n. When the fluctuation number of detectedON-status sensors decreases by three (the fluctuation number of detectedOFF-status sensors increases by three), the magazine 120 is pulled outby a three-cell distance from the library unit 100. In this case, theaddress translation field 903 in the translation information table 900therefore stores the address n+3 translated from the address n. When theON or OFF information of sensors is not changed, the magazine 120 staysin the same position. Thus the address translation field 903 in thetranslation information table 900 stores information “no addresstranslation”.

When the magazine 120 is pulled out and the sensor ON or OFF informationis detected, the accessor controller 141 calculates the fluctuationnumber of detected ON or OFF-state sensors. Then the accessor controller151 refers to the translation information 900, thereby the magnetic tapeinformation table 122 is updated automatically according to thetranslation information 900. As a result, it is possible to obtain thesame magnetic tape information table 122 as that shown in FIG. 7 in thefirst exemplary embodiment.

The address translation table 900 in this second exemplary embodiment ofthe present invention may store either the detected ON-state sensorsfield or the detected OFF-state sensors field.

As described above, the second exemplary embodiment of the presentinvention can obtain the same effects as those of the first exemplaryembodiment. In other words, even when the magazine 120 is pulled outhalfway, the position of the magazine 120 can be identified and theaccessor 140 can access any cell 110 left in the magazine 120 pulled outhalfway in the library unit 100. Furthermore, in the first exemplaryembodiment, all the possible positions of the magazine 120 to be pulledout are estimated beforehand, and the magazine position information 121and the sensor status information 123 must be stored in the memory 142.In this second embodiment, however, it is just required to store theaddress translation table 900. Thus the magnetic tape information table122 can be updated automatically with less memory capacity than in thefirst exemplary embodiment.

How to identify the position of each cell 110 in a magazine 120 is notlimited only to those described in the first and second exemplaryembodiments of the present invention. For example, it is possible thatthe memory 142 of the accessor controller 141 may store both logicaladdress table and physical address table of cells 110 and the libraryunit 100 specifies the logical address of each cell 110 in which atarget cartridge (magnetic tape) is stored. In such a case, the addresstranslation table 900 is updated automatically according to the sensorON/OFF information. And accordingly, the magnetic tape information table122 is updated automatically.

Furthermore, while a magnetic tape library unit is picked up in theembodiments of the present invention, another library unit may beemployed. The recording medium to be loaded in a cartridge is notlimited only to magnetic tape.

Furthermore, although a locking mechanism 330 and a sensor 320 areprovided at each partition 300 between cells 110 in the case of thepresent invention, the number of locking mechanisms 330 and the numberof sensors 320 may be specified freely; they are not limited only tothose in the exemplary embodiments of the present invention.

Although reflection type photosensors are employed for the magnetic tapelibrary unit of the present invention, the sensors 320 may be separatedtype photosensors. When such separated type sensors are used, the lightreceiving part of each sensor 320 is provided on the partition 300 ofthe magazine 120. However, the light receiving parts may be provided ona side surface of the magazine at equal intervals from the partition 300provided at both ends of each cell 110. On the other hand, the lightreceiving part of the sensor 325 is provided on the internal wall of thelibrary unit 102 so as to face the light receiving part of each sensor320 when the magazine 120 is loaded in the library unit 100.

While this invention has been described in conjunction with thepreferred embodiments described above, it will now be possible for thoseskilled in the art to put this invention into practice in various othermanners.

1. A library unit, comprising: a magazine loaded in said library unit; acartridge which is loaded in said magazine and arranged in a directionin which said magazine is loaded or unloaded; at least one sensorprovided for said library unit and activated to make an output, whensaid magazine is pulled out to a position other than a home position,whether or not said magazine is positioned facing said sensor; and anaccessor which identifies a position of said magazine according to anoutput of said sensor and which receives said cartridge.
 2. The libraryunit according to claim 1, further comprising: an information tableindicating a relationship between an output of said sensor and aposition of said magazine, wherein said accessor is controlled accordingto an output of said sensor and a relationship indicated in saidinformation table.
 3. The library unit according to claim 1, whereinsaid sensor comprises a reflection type photosensor.
 4. The library unitaccording to claim 1, further comprising: a plurality of magazines,wherein said accessor gives and receives said cartridge among saidplurality of magazines.
 5. The library unit according to claim 1,wherein said magazine has a partition between positions at which saidcartridges are cartridge is stored, and wherein said sensor ispositioned to face said partition when said magazine is loaded in saidlibrary unit.
 6. The library unit according to claim 5, furthercomprising: an information table indicating a relationship between theoutput of said sensor and the position of said magazine, wherein saidaccessor is controlled according to an output of said sensor and arelationship indicated in said information table.
 7. The library unitaccording to claim 5, wherein said sensor comprises a reflection typephotosensor.
 8. The library unit according to claim 5, furthercomprising: a plurality of magazines, wherein said accessor gives andreceives said cartridge among said plurality of magazines.
 9. Thelibrary unit according to claim 5, further comprising: a lockingmechanism which locks said magazine when said magazine is pulled out andsaid partition of said magazine is positioned to face said sensor,wherein said sensor detects whether or not said magazine is positionedto face said sensor when said locking mechanism is working.
 10. Thelibrary unit according to claim 9, further comprising: an informationtable indicating a relationship between the output of said sensor andthe position of said magazine, wherein said accessor is controlledaccording to an output of said sensor and a relationship indicated insaid information table.
 11. The library unit according to claim 9,wherein said sensor comprises a reflection type photosensor.
 12. Thelibrary unit according to claim 9, further comprising: a plurality ofmagazines, wherein said accessor gives and receives said cartridge amongsaid plurality of magazines.
 13. The library unit according to claim 9,further comprising: an internal plane, which is parallel to saiddirection in which said magazine is loaded or unloaded, wherein saidlocking mechanism is provided on said internal plane.
 14. The libraryunit according to claim 13, further comprising: an information tableindicating a relationship between the output of said sensor and theposition of said magazine, wherein said accessor is controlled accordingto an output of said sensor and a relationship indicated in saidinformation table.
 15. The library unit according to claim 13, whereinsaid sensor comprises a reflection type photosensor.
 16. The libraryunit according to claim 13, further comprising: a plurality ofmagazines, wherein said accessor gives and receives said cartridge amongsaid plurality of magazines.
 17. The library unit according to claim 13,wherein said magazine includes a notch, wherein said locking mechanismincludes a projection to be fit in said notch, and wherein saidprojection can move perpendicularly to said internal plane.
 18. Thelibrary unit according to claim 17, further comprising: an informationtable indicating a relationship between the output of said sensor andthe position of said magazine, wherein said accessor is controlledaccording to an output of said sensor and a relationship indicated insaid information table.
 19. The library unit according to claim 17,wherein said sensor comprises a reflection type photosensor.
 20. Thelibrary unit according to claim 17, further comprising: a plurality ofmagazines, wherein said accessor gives and receives said cartridge amongsaid plurality of magazines.
 21. The library unit according to claim 17,wherein said projection is shaped as a trapezoid of which short side isassumed at a side of a surface coming in contact with said magazine andof which long side is assumed at a side of said internal plane.
 22. Thelibrary unit according to claim 17, wherein said notch is provided forsaid partition of said magazine.
 23. The library unit according to claim22, further comprising: an information table indicating a relationshipbetween the output of said sensor and the position of said magazine,wherein said accessor is controlled according to an output of saidsensor and a relationship indicated in said information table.
 24. Thelibrary unit according to claim 22, wherein said sensor comprises areflection type photosensor.
 25. The library unit according to claim 22,further comprising: a plurality of magazines, wherein said accessorgives and receives said cartridge among said plurality of magazines. 26.The library unit according to claim 22, wherein said projection isshaped as a trapezoid of which short side is assumed at a side of asurface coming in contact with said magazine and of which long side isassumed at a side of said internal plane.
 27. The library unit accordingto claim 1, wherein said sensor is activated to make an output when saidmagazine is pulled out halfway from said library unit.
 28. The libraryunit according to claim 1, further comprising; a locking mechanism whichlocks said magazine when said magazine is pulled out to thepredetermined position, and wherein said sensor is activated to make anoutput when the locking mechanism is working.
 29. A magazine positiondetecting method in a library unit which includes a magazine loaded, acartridge, which is loaded in said magazine and arranged in a directionin which said magazine is loaded/unloaded, at least one sensor, and anaccessor for receiving said cartridge, said method comprising: making anoutput of whether or not said magazine is positioned to face said sensorby activating an output of said sensor when said magazine is pulled outto a position other than a home position; and identifying a position ofsaid magazine according to said output of said sensor to access saidcartridge.
 30. The magazine position detecting method in a library unitaccording to claim 29, wherein said library unit further includes aninformation table indicating a relationship between the output of saidsensor and the position of said magazine, said method furthercomprising: controlling said accessor according to an output of saidsensor and a relationship in said information table.
 31. The magazineposition detecting method in a library unit according to claim 29,wherein said library unit includes a plurality of magazines, said methodfurther comprising: controlling said accessor to gives and receives giveand receive said cartridge among said plurality of magazines.
 32. Themagazine position detecting method in a library unit according to claim29, wherein said magazine has a partition between positions in whichsaid cartridges are cartridge is loaded loadable respectively, saidsensor is positioned to face said partition when said magazine is loadedin said library unit, and said library unit further includes a lockingmechanism for locking said magazine when said magazine is pulled out andsaid partition of said magazine is positioned to face said sensor, saidmethod further comprising: detecting whether or not said magazine ispositioned to face said sensor when said locking mechanism is working.33. The magazine position detecting method in a library unit accordingto claim 32, wherein said library unit further includes an informationtable indicating a relationship between the output of said sensor andthe position of said magazine, said method further comprising:controlling said accessor according to an output of said sensor and arelationship in said information table.
 34. The magazine positiondetecting method in a library unit according to claim 32, wherein saidlibrary unit includes a plurality of magazines, said method furthercomprising: controlling said accessor to gives and receives give andreceive said cartridge among said plurality of magazines.
 35. Themagazine position detecting method in a library unit according to claim29, wherein said making an output is activated when said magazine ispulled out halfway from said library unit.
 36. The magazine positiondetecting method in a library unit according to claim 29, furthercomprising: working a locking mechanism which locks said magazine whensaid magazine is pulled out to the predetermined position, wherein saidsensor is activated to make an output when the locking mechanism isworking.